Transmission method, reception method, transmission apparatus, and reception apparatus

ABSTRACT

The present invention relates to transmission and reception of digital broadcast in a digital broadcast network supporting a configuration of multiple physical layer pipes (PLPs). In particular, signalling parameters relating to a complete PLP are transmitted within layer 1 signalling related to the PLP. The baseband frames mapped on the pipe are configured according to this layer 1 signalling in the same way at the transmitter as they are demapped on the receiver side. The baseband frames are transmitted and received without including these parameters, in particular, at least one of parameters indicating (i) an input stream format, (ii) a single or a multiple input stream, (iii) constant or adaptive coding and modulation, (iv) presence of input stream synchronization, (v) presence of null packet deletion, or (vi) input stream identifier.

TECHNICAL FIELD

The present invention relates to signalling in a digital broadcastnetwork. In particular, the present invention relates to layer 1 (L1)signalling and to signalling within the header of baseband frames.

BACKGROUND ART

Digital broadcast networks enable the unidirectional transmission ofdata such as audio, video, subtitling text, applications, etc. Inbroadcast networks, there is typically no return channel from thereceiver to the transmitter and thus adaptive techniques cannot beappropriately employed. At present, there are several families ofdigital broadcast standards around the world. For instance, in Europe,Digital Video Broadcasting (DVB) standards have been adopted. Ingeneral, these standards define the physical layer and the data linklayer of the broadcast distribution system. The definition of thephysical and data link layer depends on the transport medium, which canbe for instance a satellite, cable, or terrestrial channel.Correspondingly, the family of DVB standards includes DVB-S and DVB-S2for satellite transmission, DVB-C and DVB-C2 for cable transmission,DVB-T and DVB-T2 for terrestrial transmission, and DVB-H for terrestrialtransmission to handheld devices.

The recent terrestrial digital broadcast standard DVB-T2 is a successorversion of the widely used DVB-T standard in the same way as DVB-S2 andDVB-C2 are the second generation replacements of the first generationcounterparts DVB-S and DVB-C. The specifications of the two standardsfor terrestrial transmission, namely the DVB-T2 standard and the DVB-Tstandard, can be found in Non-Patent Literature 1 and Non-PatentLiterature 2, respectively. Further details and remaining DVBspecifications can be found in Non-Patent Literature 3. Other than theDVB-T standard, the DVB-T2 standard introduces, for instance, theconcept of physical layer pipes (PLP), provides new forward errorcorrection schemes, modulation constellations, larger OrthogonalFrequency Division Multiplexing (OFDM) symbol sizes and more pilotconfigurations.

The concept of physical layer pipes allows multiple parallel datastreams to be multiplexed at the physical layer. The processing for themultiple data streams may be configured separately by means ofselecting, for example, a forward error correction (FEC) coding rate,modulation constellation size, interleaving length and other physicallayer parameters. The separate configurability of the physical layerpipes enables the provision of different robustness levels for eachindividual physical layer pipe. In digital broadcasting systems that usephysical layer pipes, each service (program) can be transmitted in itsown physical layer pipe. This enables reducing the amount of data thatmust be demodulated at the receiver when assuming that only one serviceis consumed at a time, since the receiver only needs to demodulate thedata carried in the corresponding physical layer pipe. The physicallayer pipe processing includes an input processing, a forward errorcorrection (FEC) encoding, a constellation mapping, and an interleaving.Within the input processing, the user packets (stemming from TransportStreams, Generic Streams, IP streams etc.) are transformed into anappropriately formatted bitstream which is then encoded and mapped onthe physical layer resources. The input processing transforms userpackets into baseband frames. The term “user packets” used for thisinvention covers also the case of continuous streams where no packetboundaries existed or are indicated.

The basic data structure at the physical layer is known as a basebandframe. The input stream of digital broadcast data is encapsulated intobaseband frames, By applying forward error correction (FEC) to thosebaseband frames, FEC frames are formed. Baseband frames have a lengthwhich depends on the applied coding rate of the FEC coding. Basebandframes together with the parity bytes build FEC frames of fixed length,for instance, of 16,200 or 64,800 bits.

FIG. 1A illustrates the format of a baseband frame 101 with length 102of bits. The baseband frame 101 comprises a baseband frame header 110 oflength 111 (80 bits in DVB-S2, DVB-T2 and DVB-C2), a data field 120 witha data field length 121, and a padding field 130 with length 131. Thepadding field 130 may include in-band signalling information or bereplaced by in-band signalling information. The length 121 of the datafield is signalled within the baseband frame header 110. Signalling ofthe data field length (DFL) indicator 270 (cf. FIG. 2) is necessary inorder to distinguish between the data (payload) 120 transported in thebaseband frame 101 and padding field 130, which may be carried withinthe same baseband frame 101. The length 102 of the baseband frame 101corresponds to the number of bits K_(bch) to which the BCH code isapplied. The padding field 130 has a length of K_(bch)-DFL-80 bits,wherein the 80 bits correspond to the length 111 of the baseband frameheader.

Baseband frames carry the user content data and the meta-data belongingto a particular physical layer pipe of the broadcasting system. Thebaseband frames encapsulate arbitrary user packets, such as packetscarrying data coded with a compression standard such as Moving PictureExperts Group (MPEG)-2 or MPEG-4 part 10 (H.264) and encapsulated intoan MPEG transport stream, or any other packets. Moreover, the basebandframes also carry meta-data related to the content carried in the samebaseband frame. In other words, baseband frames are the outer contentencapsulation entity to which the energy dispersal scrambling as well asphysical layer error correction coding is applied. A sequence of thebaseband frames builds the content of a physical layer pipe within thebroadcasting system.

A forward error correction (FEC) frame 105 is illustrated in FIG. 1B.The forward error correction frame 105 has a length 106 of N_(ldpc)bits, and includes a baseband frame 101 with length 102 of K_(bch) bits,a field 140 with a length 141 for BCH code parity bits, and a field 150with a length 151 for parity bits of the Low Density Parity Check (LDPC)code. In the above notation, the subscript (“ldpc” or “bch”) denotes theerror correction method applied, N denotes the length of data in bitsafter applying the method in subscript, and K denotes the length of datain bits to which the subscript method is to be applied. Accordingly, thelength 141 of the LDPC parity bit field 140 corresponds toN_(bch)-K_(bch) bits. The baseband frame 101 together with the BCHparity bits 140 have a length 161 of K_(ldpc) bits to which the LDPCcode is applied which corresponds to N_(bch) bits of the BCH-encodeddata. The length 151 of the LDPC parity bit field 150 thus correspondsto N_(ldpc)-K_(ldpc) bits.

FIG. 2 illustrates a baseband frame header 201 of a normal mode and abaseband frame header 202 of a high efficiency mode defined in theDVB-T2 and -C2 specifications. DVB-S2 uses only one baseband frameformat that is identical to the normal mode format in -T2 and -C2 apartfrom the mode indication that is EXORed with the CRC-8 field in the C2and T2 cases.

The baseband frame header 201, 202 in normal mode and/or inhigh-efficiency mode includes the flowing fields.

TS/GS Indicator 210

A TS/GS indicator 210 is an input stream format indicator indicating theformat of the input stream transported by the baseband frame. The name“TS/GS” of the indicator is derived from the differentiation between atransport stream (TS) or a generic stream (GS). The length of the TS/GSindicator 210 is two bits for distinguishing the following input streamformats: a generic fixed-length packetized stream (GFPS), a transportstream (TS), a generic continual stream (GCS), and a genericencapsulated stream (GSE: generic stream encapsulation).

SIS/MIS Indicator 220

A SIS/MIS indicator 220 of one-bit length is for indicating whether asingle input stream (SIS) or multiple input streams (MIS) are carriedwithin the broadcast signal.

CCM/ACM Indicator 225

A CCM/ACM indicator 225 of one-bit length is for indicating whetherconstant coding and modulation (CCM) or adaptive coding and modulation(ACM) is applied. If constant coding and modulation is applied, allphysical layer pipes use the same coding and modulation scheme. On theother side, if variable coding and modulation is applied, then in eachphysical layer pipe the modulation and coding scheme may be configuredand it then remains constant during transmission. It may be staticallyreconfigured. In short, the configuration of whether CCM or ACM isapplied is not changed frequently.

ISSYI 230

An ISSYI 230 is an input stream synchronization indicator of a one-bitlength for indicating whether input stream synchronisation is active,i.e. whether an ISSY (input stream synchronization) field shall becomputed and inserted into the baseband frame header in the case of highefficiency mode (ISSY 231 and/or 232) or attached to each user packet(with known packet boundaries) in the case of normal mode.

NPD Indicator 240

An null packet deletion (NPD) indicator 240 is of one-bit length forindicating whether the null packet deletion is activated or not. If nullpacket deletion is activated, then the number of deleted null packets iscomputed and appended after the user packets in a field of 8 bits.

EXT Field 245

An extension (EXT) field 245 is media specific and in DVB-T2 it isnormally set to zero and reserved for future use.

ISI 250

An input stream identifier (ISI) 250 has a length of one byte. Thisfield of header is denoted as MATYPE-2. It carries ISI if the SIS/MISindicator is set to one, i.e., to a multiple input stream (MIS). If theSIS/MIS indicator is set to zero, i.e. indicates a single input stream,then the MATTYPE-2 byte is reserved for future use.

UPL Indicator 260

A user packet length indicator (UPL) 260 has a length of 16 bits andindicates user packet length in bits. UPL is not present in thehigh-efficiency mode.

DFL Indicator 270

The DFL indicator 270 is a data field length indicator of 16-bits lengthfor indicating the data field length 121 in bits of the baseband frame.

SYNC Indicator 280

A synchronization sequence (SYNC) indicator 280 is of 8 bits and notpresent in the high-efficiency mode. It is not used in genericcontinuous stream mode and copies a user packet synchronisation byteotherwise.

SYNCD Indicator 285

A SYNCD indicator 285 of 16 bits is for indicating a distance in bitsfrom the beginning of the data field 120 to the first user packet in thedata field.

CRC-8/MODE Indicator 290

A CRC-8/MODE indicator 290 of 8-bits length is for carrying errordetection parity bits for the baseband frame header and for indicatingthe BBF mode, i.e. either high efficiency or normal mode.

The first byte of the baseband frame header 201, 202 including TS/GS (2bits), SIS/MIS (1 bit), CCM/ACM (1 bit), ISSYI (1 bit), NPD (1 bit) andEXT (2 bits) fields is typically denoted as MATYPE-1 byte.

In the high-efficiency mode, the baseband frame header 202 differs fromthe baseband frame header 201 in the normal mode in that it does notcarry the UPL indicator 260 and the synchronization byte SYNC indicator280. Instead, the baseband frame header 202 can carry in thecorresponding positions an ISSY field 231, 232 (input streamsynchronization) of 24 bits. In the normal mode, the ISSY field isappended to user packets for packetized streams. In the high efficiencymode, ISSY is transmitted per baseband frame in the baseband frameheader, since the user packets of a baseband frame travel together, andtherefore experience the same delay/jitter. The high efficiency mode inthe DVB-T2 standard can thus be seen as a first attempt towards a moreefficient transport of user packets by moving particular parameters fromthe user packet headers to the baseband frame headers.

With the concept of physical layer pipes, some parameters included inthe baseband frames are already indicated by the layer 1 signalling orcould be derived from the layer 1 signalling. Indicating the sameinformation on different levels of mapping reduces the efficiency oftransmission resources utilisation. Moreover, inconsistencies may arisesuch as opposite settings for the same parameter having an equivalent,for instance, on both layer 1 signalling and signalling within thebaseband frame headers.

CITATION LIST Non Patent Literature

-   NPL 1: ETSI standard EN 302 755, “Frame Structure Channel Coding and    Modulation for a Second Generation Digital Terrestrial Television    Broadcasting System (DVB-T2)”-   NPL 2: ETSI standard ETS 300 744, “Digital Broadcasting Systems for    Television, Sound and Data Services: Frame Instructor, Channel    Coding and Modulation for Digital Terrestrial Television”-   NPL 3: ETSI World Class Standards, [available on line at    <http://www.etsi.org> as of Feb. 25, 2010]

SUMMARY OF INVENTION Technical Problem

The aim of the present invention is to improve the efficiency of thetransmission of digital broadcast data over systems with a plurality ofphysical layer pipes (including the case of a single physical layerpipe), and to prevent inconsistencies in setting the values ofcorresponding parameters differently at different protocol layers.

Solution to Problem

This is achieved by the features as set forth in the independent claims.

Preferred embodiments of the present invention form the subject matterof the dependent claims.

It is the particular approach of the present invention to signal allparameters applicable to a complete physical layer pipe only as a partof layer 1 signalling instead of providing them on a per baseband framebasis.

Providing the signalling per physical layer pipe on layer 1 requiresless transmission resources than signalling of the information in eachbaseband frame mapped to a physical layer pipe. Moreover, by signallingthe information related to a physical layer pipe only within the layer 1signalling and deriving the configuration for the baseband framesaccordingly instead of explicit signalling in the baseband frame headeravoids inconsistencies in setting corresponding parameters in differentstructures. Another advantage of the present invention lays in the factthat the robustness for the different physical layer pipes—of which oneor more carry layer 1 signalling partly or completely—as well as for thepre-amble symbols that might carry layer 1 signalling partly orcompletely can be chosen independently from each other. This is not thecase for signalling in the baseband frame headers since the robustnessof the baseband frame transmission depends on the configuration of theparticular physical layer pipe. Thus, thanks to moving a part of thebaseband frame header signalling to the layer 1 signalling, the presentinvention enables applying the desired robustness for both, content andPLP-specific signalling, separately.

In accordance with an aspect of the present invention, a method fortransmitting, in a digital broadcast network using a plurality ofphysical layer pipes (including the case of a single physical layerpipe), digital broadcast data encapsulated into one or more basebandframes is provided. Each baseband frame has a header of a predefinedformat. The physical layer forward error correction coding is applied tothe baseband frames and mapped on at least one physical layer pipe. Themethod comprises configuring a parameter of a physical layer pipe andapplying the parameter settings to each baseband frame transmittedwithin said physical layer pipe. The parameter indicates either of aninput stream format, a single or a multiple input stream, constant orvariable coding and modulation, presence of input streamsynchronization, presence of null packet deletion, or input streamidentifier. The method further includes transmitting the configuredparameter within physical layer signalling related to said physicallayer pipe, and transmitting within said physical layer pipe basebandframes that do not include in their headers the configured parameter.

In accordance with another aspect of the present invention, a method forreceiving, in a digital broadcast network using a plurality of physicallayer pipes (including the case of a single physical layer pipe),digital broadcast data encapsulated into one or more baseband frames isprovided. Each baseband frame has a header of a predefined format. Thephysical layer forward error correction coding is applied to thebaseband frames and demapped from at least one physical layer pipe. Themethod comprises receiving a parameter describing the configuration of aphysical layer pipe within layer 1 signalling related to said physicallayer pipe, the parameter indicating either of an input stream format, asingle or a multiple input stream, constant or adaptive coding andmodulation, presence of input stream synchronization, presence of nullpacket deletion, or input stream identifier. The method furthercomprises decoding the parameter of said physical layer pipe andapplying the signalled configuration to each baseband frame receivedwithin said physical layer pipe, and receiving within said physicallayer pipe baseband frames that do not include in their headers theconfigured parameter.

In accordance with still another aspect of the present invention, anapparatus is provided for transmitting, in a digital broadcast networkusing a plurality of physical layer pipes (including the case of asingle physical layer pipe), digital broadcast data encapsulated intoone or more baseband frames. Each baseband frame has a header of apredefined format. The physical layer forward error correction coding isapplied to the baseband frames and mapped on at least one physical layerpipe. The apparatus comprises a parameter setting unit for configuring aparameter of a physical layer pipe and applying the parameter settingsto each baseband frame transmitted within said physical layer pipe, theparameter indicating either of an input stream format, a single or amultiple input stream, constant or adaptive coding and modulation,presence of input stream synchronization, presence of null packetdeletion, or input stream identifier. The apparatus further comprises asignalling transmitting unit for transmitting the configured parameterwithin physical layer signalling related to said physical layer pipe,and a data transmitting unit for transmitting within said physical layerpipe baseband frames that do not include in their headers the configuredparameter.

In accordance with still another aspect of the present invention, anapparatus is provided for receiving, in a digital broadcast networkusing a plurality of physical layer pipes (including the case of asingle physical layer pipe), digital broadcast data encapsulated intoone or more baseband frames. Each baseband frame has a header of apredefined format. The physical layer forward error correction coding isapplied to the baseband frames and demapped from at least one physicallayer pipe. The receiving apparatus includes a signalling receiving unitfor receiving a parameter describing the configuration of a physicallayer pipe within physical layer signalling related to said physicallayer pipe, the parameter indicating either of an input stream format, asingle or a multiple input stream, constant or adaptive coding andmodulation, presence of input stream synchronization, presence of nullpacket deletion, or input stream identifier. The apparatus furthercomprises a PLP determining unit for decoding the parameter of saidphysical layer pipe and applying the signalled configuration to eachbaseband frame received within said physical layer pipe, and a datareceiving unit for receiving within said physical layer pipe basebandframes that do not include in their headers the configured parameter.Note that the “receiving apparatus” may be embodied as a “receiver” or a“receiving device” described below in the embodiments of the presentinvention.

Preferably, each of the parameters indicating an input stream format(220), presence of input stream synchronization, presence of NULL packetdeletion, and input stream identifier are signalled within the layer 1signalling. Carrying all these parameters within the layer 1 signallingallows for header size reduction of baseband frames, thus improvingconsiderably the transmission efficiency.

According to an embodiment of the present invention, the baseband frameheader only carries parameters indicating any of a length of thebaseband frame data field, distance to the start of the first userpacket within the baseband frame, input stream synchronization settings,or parity bits for error detection.

Preferably, the parameter indicating a single or a multiple input streamis signalled within the layer 1 as a number of physical layer pipes(PLP_NUM) and/or the parameter indicating a constant or variable codingand modulation (225) is signalled within the layer 1 as a parameter forspecifying coding rate (PLP_COD) and as a parameter for specifyingmodulation (PLP_MOD) applied to the physical layer pipe.

Advantageously, the digital broadcast network is a network based onDVB-T2 specification or its enhanced versions and the parameter issignalled within layer 1 post configurable signalling.

In accordance with another aspect of the present invention, acomputer-readable medium having a computer-readable program codeembodied thereon is provided, the program code being adapted to cause acomputer to carry out the transmission method and/or the receptionmethod according to the present invention.

The above objectives and other objectives and features of the presentinvention will become more apparent from the following description andpreferred embodiments given in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a schematic drawing illustrating the format of a basebandframe according to a DVB-T2 specification.

FIG. 1B is a schematic drawing illustrating the format of a forwarderror correction (FEC) frame according to a DVB-T2 specification.

FIG. 2 is a schematic drawing illustrating the format of a basebandframe header in a normal mode and in a high efficiency mode available inDVB-T2.

FIG. 3 is a schematic drawing illustrating layer 1 signalling accordingto DVBT2 specification.

FIG. 4 is a table illustrating the parameters of the L1-pre signallingaccording to DVB-T2 specification.

FIG. 5 is a table illustrating the parameters of the L1-postconfigurable signalling according to DVB-T2 specification.

FIG. 6 is a table illustrating the parameters of the L1-post dynamicsignalling according to DVB-T2 specification.

FIG. 7 is a schematic drawing illustrating the format of a basebandframe header in accordance with an embodiment of the present invention.

FIG. 8 is a schematic drawing illustrating an example of a digitalbroadcast system for applying the present invention.

FIG. 9 is a block diagram illustrating a transmitter and a receiveraccording to an example of the present invention.

FIG. 10 is a schematic drawing illustrating an example of a receivingdevice.

FIG. 11 is a schematic drawing illustrating the structure of multiplexeddata.

FIG. 12 is a schematic drawing illustrating how each stream ismultiplexed.

FIG. 13 is a schematic drawing illustrating in detail how a video streamis stored in a sequence of PES packets.

FIG. 14 is a schematic drawing illustrating the format of a TS packetand a source packet present in multiplexed data.

FIG. 15 is a schematic drawing illustrating the structure of PMT data.

FIG. 16 is a schematic drawing illustrating the internal structure ofmultiplexed data.

FIG. 17 is a schematic drawing illustrating the internal structure ofstream attribute information.

FIG. 18 is a schematic drawing illustrating an example of the structureof video display and audio output device.

DESCRIPTION OF EMBODIMENTS Embodiments

The present invention relates to signalling in the header of basebandframes having a fixed and configurable size and being used fortransporting content data and meta-data via communication links of adigital broadcast system. The invention also relates to the layer 1signalling in the digital broadcasting system.

The present invention provides an improved signalling related to thetransmission of data in a digital broadcast network supporting aplurality of physical layer pipes (including the case of a singlephysical layer pipe). In particular, the parameters applicable to anentire physical layer pipe are a part of the layer 1 signalling, and allbaseband frames associated with said physical layer pipe are configuredaccordingly so that no additional signalling of these parameters withinthe baseband frame header is necessary.

The following now describes embodiments of the present invention, withreference to the accompanying drawings.

Regarding the indicators (parameters) transported in the field of thebaseband frame header as illustrated in FIG. 2, most of them are commonto baseband frames within a single physical layer pipe. According to thepresent invention, such indicators (i.e., indicators or parameterscommon to baseband frames) are transmitted within a layer 1 signallingfor a physical layer pipe and applied to all baseband frames mapped onthat physical layer pipe.

Indication of particular elements being part of a physical layer pipe orsignalling of the mode of operation is not applicable to each basebandframe. Such information, generically applicable to the whole PLP, ismore suitably located within layer 1 signalling.

FIG. 3 shows the existing layer 1 signalling being part of DVB-T2. Itconsists of three elements:

-   -   P1 signalling 310 (layer 1 signalling in pre-amble symbol 1)    -   L1-pre signalling 320    -   L1-post signalling 330 (including a configurable and a dynamic        part).

A detailed description of the physical layer parameters and framestructure can be found in Non-Patent Literature 3, clause 7, which isincorporated herein by reference.

As illustrated in FIG. 3, the configured PLPs are multiplexed in thedata symbol field and P2 symbol field (if any space left) of the T2frame (transmission frame). The data length of each PLP may mutuallydiffer and is defined in the PLP loop of L1-post configurable. Each PLPis composed of one or more baseband frame of fixed length. FIG. 3illustrates a typical example in which PLP_1 includes baseband framesBBF_1, BBF_2, BBF_3 . . . and baseband flames included in the other PLPsare not illustrated.

In particular, FIG. 4 shows layer 1 pre-signalling 320 parameters. FIGS.5 and 6 show layer 1 post-signalling 330 parameters.

As can be seen from FIGS. 5 and 6, the number of PLP related attributesis signaled with the L1-post configurable part (cf. PLP loop startingwith “for i=0 . . . NUM_PLP-1” in FIG. 5).

A part of the PLP attributes is signaled in a duplicated way in L1post-configurable signalling and in the headers of the baseband framesthat are used to transport user packets through the physical layer pipesoffered by the broadcasting system.

The input stream format indicator TS/GS 210 in the baseband frame headerindicates distinction between transport streams and generic streams. Thesame distinction is also provided by a layer 1 parameter“PLP_PAYLOAD_TYPE”. In particular, the 5-bit long parameter“PLP_PAYLOAD_TYPE” distinguishes between GFPS, GCS, GSE and TS, theremaining signalling combinations are reserved for future use. Inaddition, another layer 1 parameter “TYPE” (cf. FIG. 4, L1-presignalling) specifies the types of the input streams carried in themultiplex, i.e., within the current T2 super-frame. Consequently, inaccordance with an embodiment of the present invention, the TS/GSindicator 210 is omitted from the header of baseband packets. At thereceiver, the corresponding information is determined preferably fromthe “PLP_PAYLOAD_TYPE” layer 1 parameter.

The SIS/MIS indicator 220 in the baseband frame header indicates thepresence of either a single input stream or multiple input streams. An8-bits long layer 1 parameter “NUM_PLP” (cf. FIG. 5) providesinformation about the number of physical layer pipes in the multiplex.Thus, based on the number of physical layer pipes, the indication by theSIS/MIS indicator 220 about whether there is a single input stream ormultiple input streams may be derived. In accordance with anotherembodiment of the present invention, thus, the SIS/MIS indicator 220 isno more transmitted within the baseband frame header. If the number ofphysical layer pipes indicated by “NUM_PLP”, which is one of the layer 1parameters, is 1, SIS/MIS indicator indicating single input stream isderived. Otherwise, that is, if the number of physical layer pipesindicated by “NUM_PLP”, which is one of the layer 1 parameters, is 2 orgreater, SIS/MIS indicator indicating multiple input streams is derived.In the T2 and C2 cases input streams and PLPs are identical.

The CCM/ACM indicator 225 indicates whether the modulation applied toall the PLPs included in the frame is a constant coding and modulationor advanced/variable coding and modulation. On layer 1, more detailedinformation is provided within parameters “PLP_COD” and “PLP_MOD” (cf.FIG. 5). In particular, the parameter “PLP_COD” specifies for a physicallayer pipe the code rate, and the parameter “PLP_MOD” specifies for aphysical layer pipe a modulation constellation. Thus, in accordance withyet another embodiment of the present invention, the CCM/ACM indicator225 is advantageously derived from the “PLP_COD” and “PLP_MOD”, whichare layer 1 parameters. In particular, if there are equal settings of“PLP_COD” and “PLP_MOD” for the respective configured physical layerpipes, the CCM/ACM indicator is derived to indicate constant coding andmodulation. Otherwise, that is, if the settings of “PLP_COD” for any ofthe configured physical layer pipes differs from others and/or if thesettings of “PLP_MOD” for any of the configured physical layer pipesdiffers from others, the CCM/ACM indicator is then derived to indicatevariable coding and modulation.

The input stream synchronization indicator ISSYI 230, which indicateswhether the ISSY field is valid or not, does not have an equivalent onlayer 1 so far. However, providing ISSYI 230 on baseband frame level isnot required since input stream synchronization is a PLP specificparameter, rather than a baseband frame specific parameter. Therefore,preferably, signalling of ISSYI 230 is moved from the baseband frames tolayer 1. For instance, a new parameter “PLP_ISSYI” may be included intothe PLP loop of the layer 1 post-configurable signalling part.

The NPD 240, which is an indicator of NULL packet deletion, also doesnot have an equivalent on layer 1 so far. However, since NPD is of thesame nature as ISSYI above, NPD 240 is preferably signaled withinlayer 1. For instance, a new parameter “PLP_NPDI” may be included intothe PLP loop of the layer 1 post-configurable signalling part.

An example of including the new parameters into the PLP loop shown inFIG. 5 is as follows.

for i=0..NUM_PLP−1 {   PLP_ID // 8 bit: PLP ID   PLP_PAYLOAD_TYPE // 5bit: TS, IP, etc.   ...   PLP_ISSYI // 1 bit: ISSY indication  PLP_NPDI // 1 bit: Null packet deletion indication   ...   PLP_COD //3 bit: coding   PLP_MOD // 3 bit: modulation   ... }

The field EXT 245 does not have any function assigned until now. Thus,this parameter may be removed. Instead, a signalling parameter reservedfor further use on layer 1 may be utilized in future, if necessary.

Regarding the MATYPE-2 field, the ISI 250 is an input stream identifier.It corresponds to the physical layer parameter PLP_ID (cf. FIG. 5) anduniquely identifies the physical layer pipe. A receiver can identify therelationship between the physical layer pipes and their position in thetransmission frame by means of a start address (of the first cellbelonging to the desired PLP) and the number of OFDM cells (an OFDM cellcorresponds to the modulation value for one OFDM carrier (i.e.,sub-carriers) during one OFDM symbol, e.g. a single constellation point,see e.g. Non-Patent Literature 1, clause 8) occupied by PLP. Basedthereon, a receiver can unambiguously demultiplexes the PLPs from thetransmission frames. Accordingly, it is not necessary to assign aPLP_ID/ISI to each baseband frame since each baseband frame is a part ofthe desired PLP. If a receiver need to handle different PLPs in paralleland there is a risk of mixing-up baseband frames stemming from differentPLPs, the receiver can assign PLP identifiers taken from the L1-postsignalling or assign such in an arbitrary way. Hence the MATYPE-2 fieldtogether with the input stream identifier is not required for a properoperation. According to still another embodiment of the presentinvention, MATTYPE-2 field is not transmitted in the baseband frameheader.

FIG. 7 illustrates a new baseband frame header in accordance with apreferred embodiment of the present invention. The new baseband frameheader 700 only includes the following fields.

Data Field Length Indicator DFL 270

The data field length indicator DFL 270 has a length of 16 bits andindicates the data field length.

SYNCD Field 285

The SYNCD field 285 has a length of two bytes and indicates the distanceto the first user packet in the data field 120 of the baseband frame101, wherein the distance is in bytes.

ISSY 231 and ISSY 232

The optional input stream synchronisation ISSY 231 and 232 with a lengthof 24 bits (indicated, by ISSYI within layer 1 signalling, whether ISSY231 and 232 is valid).

CRC-8 Field 295

The CRC-8 field 295 is for error detection in the baseband frame header700.

Accordingly, the size of the baseband frame header has been reduced fromthe original size of 80 bits to 64 bits. Regarding the ISSY fields 231and 232, this parameter is optional and its presence is signaledpreferably by means of layer 1 signalling.

The parameter field ISSY (3 bytes) is optional. Its presence is signaledby means of aforementioned layer 1 signalling.

The new short baseband frame header as shown in FIG. 7 will be fivebytes long in the absence of ISSY and eight bytes long in the presenceof ISSY. Even in the case that ISSY is used for lowering the jitterduring play-out, it would be sufficient to insert the correspondingfield only in the first baseband frame(s) of an interleaving frame (unitover which dynamic capacity allocation for a particular PLP is carriedout, made up of an integer, dynamically varying number of FEC frame andhaving a fixed relationship to the frames). This application wouldrequire further signalling on the layer 1 for indicating whether theISSY is present only in first baseband frames, or in each of them, orwhether it is omitted. Such a signalling may be achieved, for instance,by extending the range of the ISSYI indicator 230 signaled preferably onthe layer 1 as described above.

The present invention thus provides a higher efficiency by means oflower signalling overhead. Baseband frame headers are reduced to theabsolutely necessary number of parameter fields truly applicable on thebaseband frame level. A priori information that can be derived fromother parameters is not explicitly repeated anymore. Moreover, thepresent invention provides a correct layered approach in conformity withboth layer 1 signalling and signalling within the baseband frame headersand achieves to prevent ambiguities by avoiding signalling of redundantor duplicate information. The PLP-specific parameters are now moved tothe correct signalling layer. These are parameters that are not basebandframe specific. Parameters already existing on the correct layer 1signalling in parallel are not duplicated anymore, hence nocontradictory settings can occur anymore.

FIG. 8 shows an example of a digital broadcast system 800 in which thepresent invention may be applied. A transmitting apparatus 810 mayimplement the super-high efficiency mode (PLP_MODE) employing the shortbaseband frames of the present invention as described above, forinstance, with reference to FIG. 9, transmitter 900 a. The transmittingapparatus 810 may be a single device or a plurality of interconnecteddevices. The transmitting station 815 transmits the broadcast signalformed by the transmitting apparatus 810. In this example shown in FIG.8, a terrestrial digital broadcast system is illustrated. However, thepresent invention is not limited thereto and may also be applied to asatellite, a cable or a hybrid form of transmission (i.e. a combinationof different forms of transmission, e.g. terrestrial and satellite), orto a digital broadcast transmission over any other media. One of thereceiving apparatuses illustrated in FIG. 8 is a computer such as aportable or a personal computer 820. It may, however, be also a handhelddevice or a mobile telephone capable of receiving the digital broadcast.Another example receiving apparatuses are a set top box 830 connected toa digital or analog TV 840 or a digital TV 850 with integrated broadcastreceiver. These example receiving devices and other receiving devicescapable of receiving digital broadcast may implement the headerdecompression according to the present invention as described above, forinstance, with reference to FIG. 9, receiver 900 b.

FIG. 9 illustrates an example transmitter 900 a and receiver 900 b inaccordance with the present invention. The transmitter 900 a includes aPLP set-up unit 910, a signalling transmitting unit 920, a data mappingunit 950, and a multiplexer (MUX) 940. The receiver 900 b includes ademultiplexer (DEMUX) 960, a PLP signalling receiving unit 970, a PLPsignalling determining unit 980, and a data demapping unit 990.

The input stream data (video or audio or other) are provided to the PLPset-up unit 910 which configures the PLP(s) for the transmission ofdata. In particular, the PLP set-up unit 910 configures at least one ofthe parameters, namely the TS/GS indicator 210, SIS/MIS indicator 220,CCM/ACM indicator 225, ISSYI 230, NPD indicator 240, or ISI 250. Theconfiguration is notified to the signalling transmitting unit 920 andthe data mapping unit 950. In particular, the signalling relates to aparticular physical layer pipe used for the transmission of data, andthe data are transmitted from the data mapping unit 950 to themultiplexer 940 accordingly. In other words, the baseband frames areconfigured accordingly to be mapped on the physical layer pipe aretransmitted from the data mapping unit 950 to the multiplexer 940. Forthe transmission over the channel, the signalling and the data aremultiplexed by the multiplexer 940 to the transmission frames (e.g. T2frames). The baseband frame header data does not carry the configuredparameters.

Correspondingly, in the receiver 900 b, the demultiplexer 960demultiplexes the data and the layer 1 signalling information, and thePLP signalling receiving unit 970 receives the configured parameter(s).Then, based on the signalling information related to a particularphysical layer pipe, the signalling determining unit 980 determines theconfiguration of the received PLP and notifies the data demapping unit990 about the determined configuration of the baseband frames. Based onthe notified baseband frame configuration, the data demapping unit 990reconfigures user packets from the baseband frames included in thereceived PLP and outputs the reconfigured user packets.

That is, according to the above embodiments of the present invention. itis preferable that the PLP set-up unit 910 of the transmitter 900 aconfigures the parameters as illustrated in FIG. 7 and include theparameters in a baseband frame header and also configure the parametersas illustrated in FIG. 5 and included the parameters in the PLP loop.More preferably, the PLP set-up unit 910 configures the parameters“PLP_ISSYI” and “PLP_NPDI” in the PLP loop illustrated in FIG. 7. Eachbaseband frame included in PLP has a header of the configurationillustrated in FIG. 7 and multiplexed in the PLP. In addition, one ormore PLPs are multiplexed in the data symbols field of the frame. Thereceiver 900 b receives the frame into which one or more PLPs aremultiplexed. In each PLP, baseband frames each having a headerconfigured as illustrated in FIG. 7 are multiplexed. Note the individualindicators constituting a baseband frame are as illustrated in FIG. 7,namely the DFL 270, SYNCD 285, ISSY 231, 232, and CRC-8 295, andgenerated as described in Non-Patent Literature 2. Therefore, nodetailed description is given of how the those indicators are generated.Regarding indicators specific to each baseband frame included in a PLP,the PLP signalling determining unit 980 determines such indicators fromthe baseband frame header configured as illustrated in FIG. 7. Regardingthe rest of indicators, the PLP signalling determining unit 980determines such indicators from the PLP loop of the layer 1post-configurable signalling part (cf. FIG. 5). Still more preferably,if parameters “PLP_ISSYI” and “PLP_NPDI” described above are included inthe PLP loop, the PLP signalling determining unit 980 also uses theparameters “PLP_ISSYI” and “PLP_NPDI” to determine information specificto the baseband frames included in the PLP.

In this way, the header of each baseband frame included in PLP isreduced in length to improve the data transmission efficiency.

Another embodiment of the invention relates to the implementation of theabove described various embodiments using hardware and software. It isrecognized that the various embodiments of the invention may beimplemented or performed using computing devices (processors). Acomputing device or processor may for example be general-purposeprocessors, digital signal processors (DSP), application specificintegrated circuits (ASIC), field programmable gate arrays (FPGA) orother programmable logic devices, etc. The various embodiments of theinvention may also be performed or embodied by a combination of thesedevices.

Further, the various embodiments of the invention may also beimplemented by means of software modules, which are executed by aprocessor or directly in hardware. Also a combination of softwaremodules and a hardware implementation may be possible. The softwaremodules may be stored on any kind of computer readable storage media,for example RAM, EPROM, EEPROM, flash memory, registers, hard disks,CD-ROM, DVD, etc.

Most of the examples have been outlined in relation to a DVB-T2-baseddigital broadcasting system, and the terminology mainly relates to theDVB terminology. However, this terminology and the description of thevarious embodiments with respect to DVB-T2-based broadcasting is notintended to limit the principles and ideas of the invention to suchsystems. Also the detailed explanations of the encoding and decoding incompliance with the DVB-T2 standard are intended to better understandthe exemplary embodiments described herein and should not be understoodas limiting the invention to the described specific implementations ofprocesses and functions in the digital broadcasting. Nevertheless, theimprovements proposed herein may be readily applied in the broadcastingsystems described. Furthermore the concept of the invention may be alsoreadily used in the enhancements of DVB-T2 currently discussed instandardization.

The following describes exemplary applications of the transmission andreception methods described in the above embodiments and an exemplarystructure of a system suitable for the methods.

FIG. 10 is a schematic view illustrating an exemplary structure of areceiving device 1000 for carrying out the reception methods describedin the above embodiments. As illustrated in FIG. 10, in one exemplarystructure, the receiving device 1000 may be composed of a modem portionimplemented on a single LSI (or a single chip set) and a codec portionimplemented on another single LSI (or another single chip set). Thereceiving device 1000 illustrated in FIG. 10 is a component that isincluded, for example, in the TV (television receiver) 850, the STB (SetTop Box) 840, the computer 820, such as a personal computer, handhelddevice, or mobile telephone, illustrated in FIG. 8. The receiving device1000 includes an antenna 1060 for receiving a high-frequency signal, atuner 1001 for transforming the received signal into a baseband signal,and a demodulation unit 1002 for demodulating user packets from thebaseband signal obtained by frequency conversion. The receiver 900 bdescribed in the above embodiments corresponds to the demodulation unit1002 and executes any of the reception methods described in the aboveembodiments to receive user packets. As a consequence, the advantageouseffects of the present invention described relative to the aboveembodiments are produced.

The following description is directed to the case where received userpackets include video data and audio data. The video data has beenencoded with a moving picture coding method compliant with a givenstandard, such as MPEG2, MPEG4-Advanced Video Coding (AVC) or VC-1. Theaudio data has been encoded with an audio coding method compliant with agiven standard, such as Dolby Audio Coding (AC)-3, Dolby Digital Plus,Meridian Lossless Packing (MLP), Digital Theater Systems (DTS), DTSHD,or Pulse Coding Modulation (PCM).

The receiving device 1000 includes a stream input/output unit 1020, asignal processing unit 1004, an audio and visual output unit(hereinafter, AV output unit) 1005, an audio output unit 1006, and avideo display unit 1007. The stream input/output unit 1020 demultiplexesvideo and audio data from user packets obtained by the demodulation unit1002. The signal processing unit 1004 decodes the demultiplexed videodata into a video signal, using an appropriate moving picture decodingmethod and also decodes the demultiplexed audio data into an audiosignal using an appropriate audio decoding method. The AV output unit1005 outputs a video signal and an audio signal to an audio and visualoutput interface (hereinafter, AV output IF) 1011. The audio output unit1006, such as a speaker, produces audio output according to the decodedaudio signal. The video display unit 1007, such as a display monitor,produces video output according to the decoded video signal. Forexample, the user may operate the remote control 1050 to select achannel (of a TV program or audio broadcast), so that informationindicative of the selected channel is transmitted to an operation inputunit 1010. In response, the receiving device 1000 demodulates, fromamong signals received with the antenna 1060, a signal carried on theselected channel and applies error correction, so that reception data isextracted. At the time of data reception, the receiving device 1000receives control symbols containing information indicating atransmission method of a signal carried on the selected channel, so thatthe information indicative of the transmission method is obtained. Withthis information, the receiving device 1000 is enabled to makeappropriate settings for the receiving operation, demodulation method,and error correction method to duly receive user packets transmittedfrom a broadcast station (base station). Here, for example, symbolscarried by P1-signalling, P1-pre signalling, and L1-post signallingdescribed in the above embodiments correspond to the control symbols.Similarly, the FEC coding rate per PLP, the modulation constellation andrelated parameters contained in P1-signalling, P1-pre signalling, andL1-post signalling correspond to the information about the transmissionmethod. Although the above description is directed to an example inwhich the user selects a channel using the remote control 1050, the samedescription applies to an example in which the user selects a channelusing a selection key provided on the receiving device 1000.

With the above structure, the user can view a broadcast program that thereceiving device 1000 receives by the reception methods described in theabove embodiments.

The receiving device 1000 according to this embodiment may additionallyinclude a recording unit (drive) 1008 for recording various data onto arecording medium, such as a magnetic disk, optical disc, or anon-volatile semiconductor memory. Examples of data to be recorded bythe recording unit 1008 include data contained in user packets that areobtained as a result of demodulation and error correction by thedemodulation unit 1002, data equivalent to such data (for example, dataobtained by compressing the data), and data obtained by processing themoving pictures and/or audio. (Note here that there may be a case whereno error correction is applied to a signal obtained as a result ofdemodulation by the demodulation unit 1002 and where the receivingdevice 1000 conducts another signal processing after error correction.The same holds in the following description where similar wordingappears.) Note that the term “optical disc” used herein refers to arecording medium, such as Digital Versatile Disc (DVD) or BD (Blu-rayDisc), that is readable and writable with the use of a laser beam.Further, the term “magnetic disk” used herein refers to a recordingmedium, such as an floppy disk (FD, registered trademark) or hard disk,that is writable by magnetizing a magnetic substance with magnetic flux.Still further, the term “non-volatile semiconductor memory” refers to arecording medium, such as flash memory or ferroelectric random accessmemory, composed of semiconductor element(s). Specific examples ofnon-volatile semiconductor memory include an SD card using flash memoryand a flash solid state drive (SSD). It should be naturally appreciatedthat the specific types of recording mediums mentioned herein are merelyexamples and any other types of recording mediums may be usable.

With the above structure, the user can record a broadcast program thatthe receiving device 1000 receives with any of the reception methodsdescribed in the above embodiments, and time-shift viewing of therecorded broadcast program is possibly anytime after the broadcast. Inthe above description of the receiving device 1000, the recording unit1008 records user packets obtained as a result of demodulation and errorcorrection by the demodulation unit 1002. However, the recording unit1008 may record part of data extracted from the data contained in theuser packets. For example, the user packets obtained as a result ofdemodulation and error correction by the demodulation unit 1002 maycontain contents of data broadcast service, in addition to video dataand audio data. In this case, new user packets may be generated bymultiplexing the video data and audio data, without the contents ofbroadcast service, extracted from the user packets demodulated by thedemodulation unit 1002, and the recording unit 1008 may record the newlygenerated user packets. In another example, new user packets may begenerated by multiplexing either of the video data and audio datacontained in the user packets obtained as a result of demodulation anderror correction by the demodulation unit 1002, and the recording unit1008 may record the newly generated user packets. In yet anotherexample, the recording unit 1008 may record the contents of databroadcast service included, as described above, in the user packets.

As described above, the receiving device 1000 described in thisembodiment may be included in a TV, a recorder (such as DVD recorder,Blu-ray recorder, HDD recorder, or SD card recorder), or a mobiletelephone. In such a case, the user packets obtained as a result ofdemodulation and error correction by the demodulation unit 1002 maycontain data for correcting errors (bugs) in software used to operatethe TV or recorder or in software used to protect personal orconfidential information. If such data is contained, the data isinstalled to the TV or recorder to correct the errors. Further, if datafor correcting errors (bugs) in software installed in the receivingdevice 1000 is contained, such data is used to correct errors that thereceiving device 1000 may have. This arrangement ensures more stableoperation of the TV, recorder, or mobile phone in which the receivingdevice 1000 is implemented.

Note that it may be the stream input/output unit 1003 that performs theprocess of extracting data from the whole data contained in user packetsobtained as a result of demodulation and error correction by thedemodulation unit 1002 and then multiplexing the extracted data. Morespecifically, under instructions given from a control unit, such as CPU,not illustrated in the figures, the stream input/output unit 1003demultiplexes video data, audio data, contents of data broadcast serviceetc. from the user packets demodulated by the demodulation unit 1002,and extracts specific pieces of data from the demultiplexed data, andmultiplexes the extracted data pieces to generate new user packets. Thedata pieces to be extracted from demultiplexed data may be determined bythe user or determined in advance for the respective types of recordingmediums. With the above structure, the receiving device 1000 is enabledto extract and record only data necessary to view a recorded broadcastprogram, which is effective to reduce the size of data to be recorded.

In the above description, the recording unit 1008 records user packetsobtained as a result of demodulation and error correction by thedemodulation unit 1002. Alternatively, however, the recording unit 1008may record new user packets generated by multiplexing video data newlygenerated by encoding the original video data contained in the userpackets obtained as a result of demodulation and error correction by thedemodulation unit 1002. Here, the moving picture coding method to beemployed may be different from that used to encode the original videodata, such that the data size or bit rate of the new video data issmaller than the original video data. Here, the moving picture codingmethod used to generate new video data may be of a different standardfrom that used to generate the original video data. Alternatively, boththe moving picture coding methods may be of the same standard withdifferent parameters. Similarly, the recording unit 1008 may record newuser packets generated by multiplexing audio data newly obtained byencoding the original audio data contained in the user packets obtainedas a result of demodulation and error correction by the demodulationunit 1002. Here, the audio coding method to be employed may be differentfrom that used to encode the original audio data, such that the datasize or bit rate of the new audio data is smaller than the originalaudio data.

Note that it may be the stream input/output unit 1003 and the signalprocessing unit 1004 that perform the process of coding the originalvideo or audio data contained in the user packets obtained as a resultof demodulation and error correction by the demodulation unit 1002 intothe video or audio data of different data size or bit rate. Morespecifically, under instructions given from the control unit such asCPU, the stream input/output unit 1003 demultiplexes video data, audiodata, contents of data broadcast service etc. from the user packetsobtained as a result of demodulation and error correction by thedemodulation unit 1002. Under instructions given from the control unit,the signal processing unit 1004 encodes the demultiplexed video data andaudio data respectively using a motion picture coding method and anaudio coding method each different from the coding method used to encodethe video and audio data originally contained in the user packets. Underinstructions given from the control unit, the stream input/output unit1003 multiplexes the newly encoded video data and audio data to generatenew user packets. Note that the signal processing unit 1004 may conductthe encoding of either or both of the video or audio data according forinstructions given from the control unit. In addition, the sizes ofvideo data and audio data to be obtained by encoding may be specified bya user or determined in advance for the types of recording mediums.

With the above arrangement, the receiving device 1000 is enabled torecord video and audio data after converting the data to a sizerecordable on the recording medium or to a size or bit rate that matchesthe read or write rate of the recording unit 1008. This arrangementensures that the recoding unit duly records a broadcast program, even ifthe user packets obtained as a result of demodulation and errorcorrection by the demodulation unit 1002 are larger in size than thesize recordable on the recording medium or higher in bit rate than theread or write rate of the recording unit. Consequently, time-shiftviewing of the recorded broadcast program by the user is possibleanytime after the broadcast.

Furthermore, the receiving device 1000 additionally includes a streamoutput interface (IF) 1009 for transmitting user packets demodulated bythe demodulation unit 1002 to an external device via a transport medium1030. In one example, the stream output IF 1009 may be a radiocommunication device that transmits user packets, which are obtained bydemodulation, via a wireless medium (equivalent to the transport medium1030) to an external device, using a wireless communication methodcompliant with a wireless communication standard, such as Wi-Fi(registered trademark, a set of standards including IEEE 802.11a, IEEE802.11g, and IEEE 802.11n), WiGiG, Wireless HD, Bluetooth, or Zigbee. Inanother example, the stream output IF 1009 may be a wired communicationdevice that transmits user packets, which are obtained by demodulation,via a transmission line (equivalent to the transport medium 1030)physically connected to the stream output IF 1009 to an external device,using a communication method compliant with wired communicationstandards, such as Ethernet (registered trademark), USB (UniversalSerial Bus), PLC (Power Line Communication), or HDMI (High-DefinitionMultimedia Interface).

With the above structure, the user can use, on an external device, userpackets received by the receiving device 1000 using the reception methoddescribed according to the above embodiments. The usage of user packetsby a user mentioned herein include to use the user packet for real-timeviewing on an external device, to record the user packets by a recordingunit included in an external device, and to transmit the user packetsfrom an external device to a yet another external device.

In the above description of the receiving device 1000, the stream outputIF 1009 outputs user packets obtained as a result of demodulation anderror correction by the demodulation unit 1002. However, the receivingdevice 1000 may output data extracted from data contained in the userpackets, rather than the whole data contained in the user packets. Forexample, user packets obtained as a result of demodulation and errorcorrection by the demodulation unit 1002 contain may contain contents ofdata broadcast service, in addition to video data and audio data. Inthis case, the stream output IF 1009 may output user packets newlygenerated by multiplexing video and audio data extracted from the userpackets obtained as a result of demodulation and error correction by thedemodulation unit 1002. In another example, the stream output IF 1009may output user packets newly generated by multiplexing either of thevideo data and audio data contained in the user packets obtained as aresult of demodulation and error correction by the demodulation unit1002.

Note that it may be the stream input/output unit 1003 that handlesextraction of data from the whole data contained in user packetsobtained as a result of demodulation and error correction by thedemodulation unit 1002 and multiplexing of the extracted data. Morespecifically, the stream input/output unit 1003 demultiplexes videodata, audio data, contents of data broadcast service etc., from the userpackets demodulated by the demodulation unit 1002, and extracts specificpieces of data from the demultiplexed data, and multiplexes theextracted data pieces to generate new user packets. The data pieces tobe extracted from demultiplexed data may be determined by the user ordetermined in advance for the respective types of the stream output IF1009.

With the above structure, the receiving device 1000 is enabled toextract and output only data necessary for an external device, which iseffective to reduce the bandwidth used to output the user packets.

In the above description, the stream output IF 1009 outputs user packetsobtained as a result of demodulation and error correction by thedemodulation unit 1002. Alternatively, however, the stream output IF1009 may output new user packets generated by multiplexing video datanewly obtained by encoding the original video data contained in the userpackets obtained as a result of demodulation and error correction by thedemodulation unit 1002. The new video data is encoded with a movingpicture coding method different from that used to encode the originalvideo data, such that the data size or bit rate of the new video data issmaller than the original video data. Here, the moving picture codingmethod used to generate new video data may be of a different standardfrom that used to generate the original video data. Alternatively, thesame moving picture coding method may be used but with differentparameters. Similarly, the stream output IF 1009 may output new userpackets generated by multiplexing audio data newly obtained by encodingthe original audio data contained in the user packets obtained as aresult of demodulation and error correction by the demodulation unit1002. The new audio data is encoded with an audio coding methoddifferent from that used to encode the original audio data, such thatthe data size or bit rate of the new audio data is smaller than theoriginal audio data.

The process of converting the original video or audio data contained inthe user packets obtained as a result of demodulation and errorcorrection by the demodulation unit 1002 into the video or audio data ofdifferent data size of bit rate is performed, for example, by the streaminput/output unit 1003 and the signal processing unit 1004. Morespecifically, under instructions given from the control unit, the streaminput/output unit 1003 demultiplexes video data, audio data, contents ofdata broadcast service etc. from the user packets obtained as a resultof demodulation and error correction by the demodulation unit 1002.Under instructions given from the control unit, the signal processingunit 1004 converts the demultiplexed video data and audio datarespectively using a motion picture coding method and an audio codingmethod each different from the method that was used in the conversionapplied to obtain the video and audio data. Under instructions givenfrom the control unit, the stream input/output unit 1003 multiplexes thenewly converted video data and audio data to generate new user packets.Note that the signal processing unit 1004 may conduct the conversion ofeither or both of the video or audio data according for instructionsgiven from the control unit. In addition, the sizes of video data andaudio data to be obtained by conversion may be specified by a user ordetermined in advance for the types of the stream output IF 1009.

With the above structure, the receiving device 1000 is enabled to outputvideo and audio data after converting the data to a bit rate thatmatches the transfer rate between the receiving device 1000 and anexternal device. This arrangement ensures that even if user packetsobtained as a result of demodulation and error correction by thedemodulation unit 1002 are higher in bit rate than the data transferrate to an external device, the stream output IF duly outputs new userpackets at an appropriate bit rate to the external device. Consequently,the user can use the new user packets on another communication device.

Furthermore, the receiving device 1000 also includes the AV outputinterface 1011 that outputs video and audio signals decoded by thesignal processing unit 1004 to an external device via an externaltransport medium 1040. In one example, the AV output IF 1011 may be awireless communication device that transmits user packets, which areobtained by demodulation, via a wireless medium to an external device,using a wireless communication method compliant with wirelesscommunication standards, such as Wi-Fi (registered trademark), which isa set of standards including IEEE 802.11a, IEEE 802.11g, and IEEE802.11n, WiGiG, Wireless HD, Bluetooth, or Zigbee. In another example,the AV output IF 1011 may be a wired communication device that transmitsmodulated video and audio signals via a transmission line physicallyconnected to the AV output IF 1011 to an external device, using acommunication method compliant with wired communication standards, suchas Ethernet (registered trademark), USB, PLC, or HDMI. In yet anotherexample, the AV output IF 1011 may be a terminal for connecting a cableto output the video and audio signals in analog form.

With the above structure, the user is allowed to use on an externaldevice the video and audio signals decoded by the signal processing unit1004.

Furthermore, the receiving device 1000 additionally includes anoperation input unit 1010 for receiving a user operation. According tocontrol signals indicative of user operations input to the operationinput unit 1010, the receiving device 1000 performs various operations,such as switching the power ON or OFF, switching the currently selectedreceive channel to another channel, switching the display of subtitletext ON or OFF, switching the display of subtitle text to anotherlanguage, changing the volume of audio output of the audio output unit1006, and changing the settings of channels that can be received.

Additionally, the receiving device 1000 may have a function ofdisplaying the antenna level indicating the quality of the signal beingreceived by the receiving device 1000. Note that the antenna level is anindicator of the reception quality calculated based on, for example, theReceived Signal Strength Indication, Received Signal Strength Indicator(RSSI), received field strength, Carrier-to-noise power ratio (C/N), BitError Rate (BER), packet error rate, frame error rate, and channel stateinformation of the signal received on the receiving device 1000. Inother words, the antenna level is a signal indicating the level andquality of the received signal. In this case, the demodulation unit 1001also serves the function of a reception quality measuring unit formeasuring the received signal characteristics, such as RSSI, thereceived field strength, C/N, BER, packet error rate, frame error rate,and channel state information. In response to a user operation, thereceiving device 1000 displays the antenna level (i.e., signalindicating the level and quality of the received signal) on the videodisplay unit 1007 in a manner identifiable by the user. The antennalevel (i.e., signal indicating the level and quality of the receivedsignal) may be numerically displayed using a number that represents theRSSI, received field strength, C/N, BER, packet error rate, frame errorrate, channel state information or the like. Alternatively, the antennalevel may be displayed using an image representing the RSSI, receivedfield strength, C/N, BER, packet error rate, frame error rate, channelstate information or the like.

Although the receiving device 1000 is described above as having theaudio output unit 1006, video display unit 1007, recording unit 1008,stream output IF 1009, and AV output IF 1011, it is not necessary thatthe receiving device 1000 has all of these units. As long as thereceiving device 1000 is provided with at least one of the units1006-1011 described above, the user is enabled to use user packetsobtained as a result of demodulation and error correction by thedemodulation unit 1002. It is therefore applicable that the receivingdevice 1000 has one or more of the above-described units in anycombination depending on its application.

User Packets

The following is a detailed description of an exemplary structure of auser packet. The data structure typically used in broadcasting is anMPEG2 transport stream (TS), so that the following description is givenby way of an example related to MPEG2-TS. It should be naturallyappreciated, however, that the data structure of user packetstransmitted by the transmission and reception methods described in theabove embodiments is not limited to MPEG2-TS and the advantageouseffects of the above embodiments are achieved even if any other datastructure is employed.

FIG. 11 is a view illustrating an exemplary user packet structure. Asillustrated in FIG. 11, a user packet is obtained by multiplexing one ormore of elementary streams, which are elements constituting a broadcastprogram (program or an event which is part of a program) currentlyprovided through respective services. Examples of elementary streamsinclude a video stream, audio stream, presentation graphic (PG) stream,and interactive graphic (IG) stream. In the case where a broadcastprogram carried by user packet(s) is a movie, the video streamsrepresent main video and sub video of the movie, the audio streamsrepresent main audio of the movie and sub audio to be mixed with themain audio, and the PG stream represents subtitles of the movie. Theterm “main video” used herein refers to video images normally presentedon a screen, whereas “sub video” refers to video images (for example,images of text explaining the outline of the movie) to be presented in asmall window inserted within the video images. The IG stream representsan interactive display constituted by presenting GUI components on ascreen.

Each stream contained in a user packet is identified by an identifiercalled PID uniquely assigned to the stream. For example, the videostream carrying main video images of a movie is assigned with “0x1011”,each audio stream is assigned with a different one of “0x1100” to“0x111F”, each PG stream is assigned with a different one of “0x1200” to“0x121F”, each IG stream is assigned with a different one of “0x1400” to“0x141F”, each video stream carrying sub video images of the movie isassigned with a different one of “0x1B00” to “0x1B1F”, each audio streamof sub-audio to be mixed with the main audio is assigned with adifferent one of “0x1A00” to “0x1A1F”.

FIG. 12 is a schematic view illustrating an example of how therespective streams are multiplexed into a user packet. First, a videostream 1201 composed of a plurality of video frames is converted into aPES packet sequence 1202 and then into a TS packet sequence 1203,whereas an audio stream 1204 composed of a plurality of audio frames isconverted into a PES packet sequence 1205 and then into a TS packetsequence 1206. Similarly, the PG stream 1211 is first converted into aPES packet sequence 1212 and then into a TS packet sequence 1213,whereas the IG stream 1216 is converted into a PES packet sequence 1212and then into a TS packet sequence 1216. The user packets 1217 areobtained by multiplexing the TS packet sequences (1203, 1206, 1213 and1216) into one stream.

FIG. 13 illustrates the details of how a video stream is divided into asequence of PES packets. In FIG. 13, the first tier shows a sequence ofvideo frames included in a video stream. The second tier shows asequence of PES packets. As indicated by arrows yy1, yy2, yy3, and yy4shown in FIG. 13, a plurality of video presentation units, namely Ipictures, B pictures, and P pictures, of a video stream are separatelystored into the payloads of PES packets on a picture-by-picture basis.Each PES packet has a PES header and the PES header stores aPresentation Time-Stamp (PTS) and Decoding Time-Stamp (DTS) indicatingthe display time and decoding time of a corresponding picture.

FIG. 14 illustrates the format of a TS packet to be eventually loaded toa user packet. The TS packet is a fixed length packet of 188 bytes andhas a 4-byte TS header containing such information as PID identifyingthe stream and a 184-byte TS payload carrying actual data. The PESpackets described above are divided to be stored into the TS payloads ofTS packets. In the case of BD-ROM, each TS packet is attached with a TPextra header of 4 bytes to build a 192-byte source packet, which is tobe loaded to a user packet. The TP extra header contains suchinformation as arrival time stamp (ATS). The ATS indicates a time forstarring transfer of the TS packet to the PID filter of a decoder. Asshown on the lowest tier in FIG. 14, a user packet includes a sequenceof source packets each bearing a source packet number (SPN), which is anumber incrementing sequentially from the start of the user packet.

In addition to the TS packets storing streams such as video, audio, andPG streams, a user packet also includes TS packets storing a ProgramAssociation Table (PAT), a Program Map Table (PMT), and a Program ClockReference (PCR). The PAT in a user packet indicates the PID of a PMTused in the user packet, and the PID of the PAT is “0”. The PMT includesPIDs identifying the respective streams, such as video, audio andsubtitles, contained in a user packet and attribute information (framerate, aspect ratio, and so on) of the streams identified by therespective PIDs. In addition, the PMT includes various types ofdescriptors relating to the user packet. One of such descriptors may becopy control information indicating whether or not copying of the userpacket is permitted. The PCR includes information for synchronizing theArrival Time Clock (ATC), which is the time axis of ATS, with the SystemTime Clock (STC), which is the time axis of PTS and DTS. Morespecifically, the PCR packet includes information indicating an STC timecorresponding to the ATS at which the PCR packet is to be transferred.

FIG. 15 is a view illustrating the data structure of PMT in detail. ThePMT starts with a PMT header indicating the length of data contained inthe PMT. Following the PMT header, descriptors relating to the userpacket are disposed. One example of a descriptor included in the PMT iscopy control information described above. Following the descriptors,pieces of stream information relating to the respective streams includedin the user packet are arranged. Each piece of stream information iscomposed of stream descriptors indicating a stream type identifying acompression codec employed for a corresponding stream, a PID of thestream, and attribute information (frame rate, aspect ratio, and thelike) of the stream. The PMT includes as many stream descriptors as thenumber of streams included in the user packet.

When recorded onto a recoding medium, for example, the user packet isrecorded along with a user packet information file.

FIG. 16 is a view illustrating the structure of the user packetinformation file. As illustrated in FIG. 16, the user packet informationfile is management information of a corresponding user packet andcomposed of user packet information, stream attribute information and anentry map. Note that user packet information files and user packets arein a one-to-one relationship.

As illustrated in FIG. 16, the user packet information is composed of asystem rate, playback start time, and playback end time. The system rateindicates the maximum transfer rate of the user packet to the PID filterof a system target decoder, which will be described later. The userpacket includes ATSs at intervals set so as not to exceed the systemrate. The playback start time is set to the time specified by the PTS ofthe first video frame in the user packet, whereas the playback end timeis set to the time calculated by adding the playback period of one frameto the PTS of the last video frame in the user packet.

FIG. 17 illustrates the structure of stream attribute informationcontained in a user packet information file. As illustrated in FIG. 17,the stream attribute information includes pieces of attributeinformation of the respective streams included in a user packet and eachattribute information is registered with a corresponding PID. That is,different pieces of attribute information are provided for differentstreams, namely a video stream, an audio stream, a PG stream and an IGstream. The video stream attribute information indicates the compressioncodec employed to compress the video stream, the resolutions ofindividual pictures constituting the video stream, the aspect ratio, theframe rate, and so on. The audio stream attribute information indicatesthe compression codec employed to compress the audio stream, the numberof channels included in the audio stream, the language of the audiostream, the sampling frequency, and so on. These pieces of informationare used to initialize a decoder before playback by a player.

In the present embodiment, from among the pieces of information includedin the user packet information file, the stream type included in the PMTis used. In the case where the user packet is recorded on a recordingmedium, the video stream attribute information included in the userpacket information file is used. More specifically, the moving picturecoding method and device described in any of the above embodiments maybe modified to additionally include a step or unit of setting a specificpiece of information in the stream type included in the PMT or in thevideo stream attribute information. The specific piece of information isfor indicating that the video data is generated by the moving picturecoding method and device described in the embodiment. With the abovestructure, video data generated by the moving picture coding method anddevice described in any of the above embodiments is distinguishable fromvideo data compliant with other standards.

FIG. 18 illustrates an exemplary structure of a video and audio outputdevice 1800 that includes a receiving device 1804 for receiving amodulated signal carrying video and audio data or data for databroadcasting from a broadcasting station (base station). Note that thestructure of the receiving device 1804 is basically same as thereceiving device 1000 illustrated in FIG. 10. The video and audio outputdevice 1800 is installed with an Operating System (OS), for example, andalso with a communication unit 1806 (a device for wireless Local AreaNetwork (LAN) or Ethernet (registered trademark), for example) forestablishing Internet connection. With this structure, hypertext (WorldWide Web (WWW)) 1803 provided over the Internet can be displayed on adisplay area 1801 simultaneously with images 1802 reproduced on thedisplay area 1801 from the video and audio data or data provided by databroadcasting. By operating a remote control (which may be a mobile phoneor keyboard) 1807, the user can make a selection on the images 1802reproduced from data provided by data broadcasting or the hypertext 1803provided over the Internet to change the operation of the video andaudio output device 1800. For example, by operating the remote controlto make a selection on the hypertext 1803 provided over the Internet,the user can change the WWW site currently displayed to another site.Alternatively, by operating the remote control 1807 to make a selectionon the images 1802 reproduced from the video or audio data or dataprovided by the data broadcasting, the user can transmit informationindicating the selected channel (such as selected broadcast program oraudio broadcasting). In response, an interface (IF) 1805 acquiresinformation transmitted from the remote control 1807, so that thereceiving device 1804 operates to obtain reception data by demodulationand error correction of a signal carried on the selected channel. At thetime of data reception, the receiving device 1804 receives controlsymbols containing information indicating a transmission method of asignal carried on the selected channel, so that the informationindicative of the transmission method is obtained. With the information,the receiving device 1804 is enabled to make appropriate settings forthe receiving operation, demodulation method, and error correctionmethod to duly receive user packets transmitted from a broadcast station(base station). Although the above description is directed to an examplein which the user selects a channel using the remote control 1807, thesame description applies to an example in which the user selects achannel using a selection key provided on the video and audio outputdevice 1800.

In addition, the video and audio output device 1800 may be operated viathe Internet. (The video and audio output device 1800 therefore has therecording unit 1008 as illustrated in FIG. 10.) Before starting thepre-programmed recording, the video and audio output device 1800 selectsthe channel, so that the receiving device 1804 operates to obtainreception data by demodulation and error correction of a signal carriedon the selected channel. At the time of data reception, the receivingdevice 1804 receives control symbols containing information indicating atransmission method of a signal carried on the selected channel, so thatthe information indicative of the transmission method is obtained. Withthe information, the receiving device 1804 is enabled to makeappropriate settings for the receiving operation, demodulation method,and error correction method to duly receive user packets transmittedfrom a broadcast station (base station).

Summarizing, the present invention relates to transmission and receptionof digital broadcast in a digital broadcast network supporting aconfiguration of a single or multiple physical layer pipes. Inparticular, according to the present invention, signalling parametersrelating to PLP are transmitted within layer 1 signalling related to thePLP. The baseband frames mapped on the PLP are configured according tothis layer 1 signalling in the same way at the transmitter and thereceiver. The baseband frames are transmitted and received withoutincluding these parameters, in particular, at least one of parametersindicating (i) an input stream format, (ii) a single or a multiple inputstream, (iii) constant or adaptive coding and modulation, (iv) presenceof input stream synchronization, (v) presence of null packet deletion,or (vi) input stream identifier.

INDUSTRIAL APPLICABILITY

The present invention is useful in particular in a digital broadcastingsystem capable of data transmission using multiple PLPs.

REFERENCE SIGNS LIST

-   -   800 digital broadcast system    -   810 transmitting apparatus    -   815 transmitting station    -   820 personal computer (PC)    -   830 set top box (STB)    -   840 digital or analog TV    -   850 digital TV with integrated broadcast receiver    -   900 a transmitter    -   900 b receiver    -   910 PLP set-up unit    -   920 signalling transmitting unit    -   940 multiplexer    -   950 data mapping unit    -   960 demultiplexer    -   970 PLP signalling receiving unit    -   980 PLP signalling determining unit    -   990 data demapping unit    -   1000 receiving device    -   1001 tuner    -   1002 demodulation unit    -   1003 stream input/output unit    -   1004 signal processing unit    -   1005 audio and visual (AV) output unit    -   1006 audio output unit    -   1007 video display unit    -   1008 recording unit    -   1009 stream output interface (interface) IF    -   1010 operation input unit    -   1011 audio and visual interface (AV output IF)    -   1030, 1040 medium    -   1050 remote control    -   1800 video and audio output device    -   1801 display area    -   1802 images    -   1803 hypertext    -   1804 receiving device    -   1805 interface (IF)    -   1806 communication unit    -   1807 remote control

The invention claimed is:
 1. A method for transmitting, in a digitalbroadcast network supporting a configuration of a plurality of physicallayer pipes, digital broadcast data encapsulated into one or morebaseband frames each with a header of a predefined format, the basebandframes being the frames to which physical layer forward error correctioncoding is applied and that are mapped on at least one physical layerpipe, the method comprising the steps of: configuring one or moreparameters of a physical layer pipe; transmitting the configuredparameters within physical layer signaling related to said physicallayer pipe; and transmitting, within said physical layer pipe basebandframes, the header of each baseband frame including parametersindicating at least one of a length of a baseband payload and a distanceto a start of a first user packet within the baseband frame, and notincluding a parameter indicating an input stream identifier andparameters indicating at least two of an input stream format, a singleor a multiple input stream, constant or adaptive coding and modulation,presence of input stream synchronization, and presence of null packetdeletion, wherein the physical layer signaling at least includes theparameters that are not included in the header of each baseband frameindicating said at least two of an input stream format, a single or amultiple input stream, constant or adaptive coding and modulation,presence of input stream synchronization, and presence of null packetdeletion.
 2. A method for receiving, in a digital broadcast networksupporting a configuration of a plurality of physical layer pipes,digital broadcast data encapsulated into one or more baseband frameseach with a header of a predefined format, the baseband frames being theframes to which physical layer forward error correction coding isapplied and that are demapped from at least one physical layer pipe, themethod comprising the steps of: receiving one or more parametersdescribing the configuration of a physical layer pipe within physicallayer signaling related to said physical layer pipe; decoding theparameters describing the configuration of said physical layer pipe andapplying the signaled configuration to each baseband frame receivedwithin said physical layer pipe; and receiving, within said physicallayer pipe baseband frames, the header of each baseband frame includingparameters indicating at least one of a length of a baseband payload anda distance to a start of a first user packet within the baseband frame,and not including a parameter indicating an input stream identifier andparameters indicating at least two of an input stream format, a singleor a multiple input stream, constant or adaptive coding and modulation,presence of input stream synchronization, and presence of null packetdeletion, wherein the physical layer signaling at least includes theparameters that are not included in the header of each baseband frameindicating said at least two of an input stream format, a single or amultiple input stream, constant or adaptive coding and modulation,presence of input stream synchronization, and presence of null packetdeletion.
 3. An apparatus for transmitting, in a digital broadcastnetwork supporting a configuration of a plurality of physical layerpipes, digital broadcast data encapsulated into one or more basebandframes each with a header of a predefined format, the baseband framesbeing the frames to which physical layer forward error correction codingis applied and that are mapped on at least one physical layer pipe, theapparatus comprising: a parameter setting unit for configuring one ormore parameters of a physical layer pipe; a signaling transmitting unitfor transmitting the configured parameters within physical layersignaling related to said physical layer pipe; and a data transmittingunit for transmitting, within said physical layer pipe baseband frames,the header of each baseband frame including parameters indicating atleast one of a length of a baseband payload and a distance to a start ofa first user packet within the baseband frame, and not including aparameter indicating an input stream identifier and parametersindicating at least two of an input stream format, a single or amultiple input stream, constant or adaptive coding and modulation,presence of input stream synchronization, and presence of null packetdeletion, wherein the physical layer signaling at least includes theparameters that are not included in the header of each baseband frameindicating said at least two of an input stream format, a single or amultiple input stream, constant or adaptive coding and modulation,presence of input stream synchronization, and presence of null packetdeletion.
 4. An apparatus for receiving, in a digital broadcast networksupporting a configuration of a plurality of physical layer pipes,digital broadcast data encapsulated into one or more baseband frameseach with a header of a predefined format, the baseband frames being theframes to which physical layer forward error correction coding isapplied and that are demapped from at least one physical layer pipe, theapparatus comprising: a signaling receiving unit for receiving one ormore parameters describing the configuration of a physical layer pipewithin physical layer signaling related to said physical layer pipe; aPLP determining unit for decoding the parameters describing theconfiguration of said physical layer pipe and applying the signaledconfiguration to each baseband frame received within said physical layerpipe; and a data receiving unit for receiving, within said physicallayer pipe baseband frames, the header of each baseband frame includingparameters indicating at least one of a length of a baseband payload anda distance to a start of a first user packet within the baseband frame,and not including a parameter indicating an input stream identifier andparameters indicating at least two of an input stream format, a singleor a multiple input stream, constant or adaptive coding and modulation,presence of input stream synchronization, and presence of null packetdeletion, wherein the physical layer signaling at least includes theparameters that are not included in the header of each baseband frameindicating said at least two of an input stream format, a single or amultiple input stream, constant or adaptive coding and modulation,presence of input stream synchronization, and presence of null packetdeletion.